This invention relates generally to communications and, more particularly, to packet communications systems.
One use of the Internet as a communications vehicle is as an enhanced data backbone for coupling together workgroups to provide what is referred to as a xe2x80x9cvirtual private networkxe2x80x9d (VPN). One application of a VPN is in a corporate environment such that employees, e.g., at home, can remotely access, via the Internet, corporate data networks. A VPN provides security, and authentication, for a remote user to join a closed user group notwithstanding the use of public facilities. In effect, the use of a VPN provides a WAN-like vehicle to the corporation and its employees. (Although the corporate network could also provide direct remote access, e.g., a user dials directly into the corporate network, there are economic advantages to the use of a VPN.)
To provide a VPN, tunneling protocols are used such as the xe2x80x9cPoint-to-Point Tunneling protocolxe2x80x9d (PPTP) and the xe2x80x9cLayer 2 Forwardingxe2x80x9d (L2F) protocol. Generally speaking, a tunnel protocol enables the creation of a private data stream via a public network by placing one packet inside of another. In the context of a VPN, an IP packet is placed inside another IP packet. In an attempt to develop an industry standard, the Internet Engineering Task Force (IETF) is developing the xe2x80x9cLayer 2 Tunneling Protocolxe2x80x9d (L2TP), which is a hybrid of the PPTP and L2F protocols (e.g., see K. Hamzeh, T. Kolar, M. Littlewood, G. Singh Pall, J. Taarud, A. J. Valencia, W. Verthein; Layer Two Tunneling Protocol xe2x80x9cL2TPxe2x80x9d; Internet draft, March, 1998).
For a remote user, a typical form of access to a VPN is via a xe2x80x9cplain-old-telephone servicexe2x80x9d (POTS) connection to an xe2x80x9cInternet service providerxe2x80x9d (ISP) that provides the VPN service. For example, a user incorporates an analog modem into a personal computer, or equivalent, and has a customer account with a particular ISP, referred to herein as the xe2x80x9chomexe2x80x9d ISP. (It is also assumed that the user""s personal computer is properly configured to support one of the above-mentioned tunneling protocols.) The user accesses the VPN by simply making a data call to the home ISP, e.g., dialing a telephone number associated with the xe2x80x9chomexe2x80x9d ISP and then xe2x80x9clogging inxe2x80x9d to the VPN.
Access to an ISP is via a network access server (NAS). We have realized that in a Personal Communications Service (PCS) wireless environment the above-described tunneling protocols do not allow a remote user, on an existing call, to change the NAS that is providing access to a VPN. As such, the user""s physical mobility may disconnect, or drop, the user from the existing VPN connection.
Therefore, and in accordance with the invention, an NAS or LAC incorporates a xe2x80x9chand-offxe2x80x9d feature that allows an existing PPP connection to be transferred from one NAS to another NAS.
In an embodiment of the invention, 3 new control messages are defined for use in an NAS. Namely: (i) Continued Call Request, (ii) Continued Call Reply, and (iii) Continued Call Connect. These 3 new control messages comprise a L2TP control message header, message identifier (e.g., continued call request, etc.), and a number of fields.
As a result of the above, the user does not have to terminate the current PPP connection and then re-establish a new PPP connection.